Sequential access data store



6 Sheets-Sheet l L f. mmfwMM/W, ,a Zwww WCM/. .f hf J a @dew M L WM M Q KAWMU y M.C.LENBERGER ETAL SEQUENTIAL ACCESS DATA STORE July 4, 1967 Original Filed June 30. 196C July 4, 1967 M. c. LEINBERGER ETAL 3,329,944

SEQUENTIAL ACCESS 'DATA STORE Original Filed June 30. 1960 6 Sheets-Sheet 2 a@ wafer/@d 74a lle far/perfo# 00e Mrd Wer/'ad L ne Ward ,per/'al July 4, 1967 Mfc. LE1NBERGER ETAL 3,329,944

SEQUENTIAL ACCESS DATA STORE Original Filed June 30. 1960 6 Sheets-Sheet 5 ,6e/arf; Pdve/ Fard/47d 22 Trax/a (C) A n@ 'A' if?) I "fr July 4, 1967 M. C, LEINBERGER ETAL SEQUENTIAL ACCESS DATA STORE 6 Sheets-Sheet 4 Original Filed June 50. 1960 L t .m

July 4, 1967 M. C. LEINBERGER ETAL SEQUENTIAL ACCESS DATA STORE 6 Sheets-Sheet 5 Original Filed June 50, 1960 WN) QM.

July 4, 1967 M. c. LEINBERGER :TAL 3,329,944

SEQUENTIAL ACCESS DATA STORE Original Filed June .'50, 1960 A 6 Sheets-Sheet 6 179 j 32 i 23 173 I 1 e y l l l E 15a 154 'l 1 1 l i 165 152 'f5 l 156 f5? /faf i4 1 f 17a l 24 r l 27 s fr| I 145 ci l j 172 174 I f 1 I if :Jill y? 2 xl l j 2 171 i 'l d L` I a i; 130

2a l l 2 l i3 i 173 I 145' f" 2, i 146 i f4; f f 149 I? Il 142 s f"' L l// I i l` A l f v I Y v j United States Patent O 3,329,944 SEQUENTIAL ACCESS DATA STORE Merton C. Leinberger, Inglewood, Cecil H. Burns, Palo Yerdes, and Robert A. Melnick, Los Angeles, Calif., asslgnors to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Continuation of application Ser. No. 39,943, June 30, 1960. This application June 6, 1966, Ser. No. 555,942 Claims. (Cl. S40-174.1)

This application is a continuation of Application 39,943 tiled J une 30, 1960, and now abandoned.

The present invention relates to sequentially accessed cyclical data stores, and more particularly to the prov1s1on of apparatus for utilizing helical recording tracks on the surface of a rotating memory unit to provide an endless or continuous data storage channel.

It'is highly desirable in data processing systems to provide sequentially accessed cyclical data stores having a large storage capacity. By use of such apparatus, stored coded data corresponding to a large number of business transactions can continuously and repeatedly be made available for simple manipulation, as the data serially read from the store is passed into a computing network, for example. Although -a circumferential storage channel on a rotating drum with a single stationary transducer cooperating therewith has in the past been made available for such purposes, as the required capacity of the storage channel increases, an increase in the diameter of the drum is required. Such an approach thus becomes 'impractical when -a continuous large capacity storage channel is required equivalent to many times the capacity of a channel provided by a single revolution `of the drum.

In the preferred embodiment of the invention, a movable record member, in the form of a drum, having a plurality of annular sections capable of storing bits of binanry data, is rotated to pass each annular section through a respective operating zone extending across the respective section. A plurality of transducers are supported for transverse movement in respective operating zones to cooperate with respective annular sections for reading and recording data in said sections. The movement of the transducers is produced and controlled by operating means individually coupled to each transducer,

-for producing individual cyclical movements of the trans-V ducers in respective operating zones in which the cyclical movements have a predetermined out of phase relationship -Whereby the annular sections are alternately traversed by the transducers along respective helical data storage tracks.V

In the preferred arrangement, the helical tracks in the respective sections are traced by the respective transducers while the transducers are in the forward travel portion of their individual cycles and traveling at a uniform rate in order to follow or trace uniform helical paths in the respective sections'. In order to provide sequential operation of the transducers without interruption, the cycles of motion of the transducers have a predetermined out-of-phase relationship whereby the forward travel portions of the cycles of motion for the transducers are successive and preferably overlapping to assure a continuous channel for the storage of data. During the intervals of overlap of the forward travel of the transducers when either transducer is approaching the end of its forward travel and the other transducer is just beginning its forward travel and both are moving at a uniform rate, the connections of the read-Write circuitry are switched from the transducer approaching the end of its forward travel to the transducer beginning its forward travel. The rotation of the drum and the movement of the transducers is coordinated and timing signals, indicating the positions of the transducers and the start of each cycle of the drum 3,329,944 Patented July 4, 1967 are coupled to signal circuits connected to the transducers to synchronize the switching from one transducer to the other when either transducer reaches the end of its respective data storage track and the other transducer reaches the beginning of its respective data track.

Accordingly, one of the objects of this invention is to provide a highly compact, large capacity sequentially accessed data storage channel on a rotating storage unit whose capacity is equal to the length of the path provided by a plurality of revolutions of the storage unit.

Another object of the invention is to provide a continuous data store by utilizing a plurality of helical recording paths provided on the surface of a rotating memory.

Another object of the present invention is to provide for moving a plurality of transducers across the surface of a rotating storage unit so as to provide helical -recording paths and for switching the operation of the transducers to effectively connect the ends of the helical recording paths to form Ian endless or continuous storage channel.

Still yanother object of the invention is to provide for simultaneously reading .and Writing data on an endless data storage channel formed along helical recording paths provided on the surface of a rotating drum memory.

A still further object is to provide for synchronizing the switching of the operation of respective read and Write heads in a plurality of transducers tracing respective helical data storage tracks on a rotating memory to thereby provide for simultaneously reading and writing data on a continuous dat-a storage channel.

A still further object of the invention is to form a. continuous data storage channel on the surface of a rotating drum by providing a pair of cyclically moving transducers each following a respective helical recording track on the rotating surface, which track is -retraced on successive phases of the -respective transducers along the rotating surface.

Other object-s and features of the invention will become apparent to those skilled in the art as the disclosure is made in the following -detailed description of a preferred embodiment of the invention as illustrated in the accompanying sheets of drawings in which:

FIG. 1 is a schematic illustration, partly in block diagram, of the preferred embodiment of the invention;

FIG. 2a illustrates a data storage-drum of the preferred embodiment schematically, in which the longitudinal dimension of the drum has been exaggerated and portions have been broken away to permit the data tracks to be indicated schematically on the outer annular periphery of the drum;

FIG. 2b is a timing diagram of the movements of the transducers;

FIGS. 3 and 4 are idealized waveforms of typical signals produced in the operation of the invention;

FIG. 5 is a top view of the apparatus included in the preferred embodiment of the invention;

FIG. 6 is a side view of the apparatus shown in FIG. 5;

FIG. 7 is a perspective view of the transducer and operating mechanism of the preferred embodiment of the invention.

Referring to FIG. 1, in which the preferred embodiment for providing a continuous data storage channel in a sequential access data store has been illustrated schematically, a rotatable data storage drum 10 is shown mounted coaxially on a vertical drive shaft 12. The outer annular periphery 16 of the drum 10 includes lower and upper annular sections 18 and 22 which are capable of storing bits of binary data. A motor 14 is the primary source of drivin-g power and is coupled to the shaft 12 for rotating the drum 10 about its axis.

During rotation of the drum 10, the lower and upper sections 18 and 22. Transducers 20 and 24 are disposedV vadjacent the annular periphery 16 and supported for movement in a direction which is transverse to the direction i of rotational movement of the annular sections 18 and 22,

whereby rectilinear movementV of the transducers'20 and 24, during their upward travel only, traverses respective annular sections 18 and 22 'of the rotating drum along helical tracks 40 and 42 respectively, as shown in FIG. 2a. TheV movable transducers 20 and 24 are coupled to an 'operating' mechanism 27 which produces phased cyclical rectilinear movements of the transducers for traversing the respective annular sections 18 and 22 in respective transverse operating zones 21 and 25. The operating mechanism 27 comprises, in addition to other apparatus, a pair of disc cams 26 and 30 having identical profiles but disposed 180 out of phase. The disc cams 26 and Q30 are coupled to respective transducers 20 and 24 by cam follower means, which in FIG. 1 is indicated by the schematically depicted camfollower rods 278 and 32, lrespectively. The cams 26 :and 30 areamounted on a cam shaft 34 coupled to the motor 14 by Ya reduction gear train 36 to rotate the cam shaft at a reduced speed which i is coordinated with the speed of rotation of the drum .in order to retrace helical paths on the respective annular `sections 1-8 andV 22 in successive Vupward movementsor forward traversals of thesections by the respectivermovable transducers and 24. "i Y I Phased cyclical movements of the transducers 20 and 24, by the operating mechanism 27 in respective operating zones 21 and 25, is depictedbyV the curves 51V and 53 in the timing diagram of FIG. V2b inwhich the individ- -ual but coordinated cylical movements of the'movable transducers in respective operating zones are indicated separately on the vertical axis of the diagram while; the number of revolutions of the drum 10 is indicatedon a common horizontal axis. Areas 18' and 22 correspond to lowerV and upper sections 18 and 22, respectively of the Y drum 10. As shown, the cycles of/.motion of the transducers ane identical, but shifted'in phase substantially 180. The rate of the return travel of the `transducers 20 and 24 is at a faster rate than the rate of forward travel. The accelerated return travel provides a time period in which the returning transducer can be placed in motion ata uniform rate in the forward travel portion of its cycle, before the other transducer has completed its forward travel at the same uniform rate. During the time period that bot-h transducers 20 and 24 arel in the A Yforward travel portion of their respective cycles, and both are moving at the Ysame uniform rate, the read-Write circuitry (FIG. 1) is switched Afrom the transducer ending its forward travel to the. transducer beginning its forward travel to provide -for Aan'uninterrupted ow of read `signals to a common read signal output and Ywrite'signals from a commoniwrite signal input to the transducers. Thus, a returning transducer is positioned at the lower edge of the respective annular section of the drum 10 for forward travel near the end of the forward travel of i Y the other transducer to provide continuity between foranism 27, and consequently, the movements of the movable transducers 20 and 24 with the rotational movement of the drum 10, results in tracing and retracing the same helical paths or tracks 40 and 42, illustrated in FIG. 2a, by the respective transducers 20 and 24 which alternately, without interruption traverse their respective sections while in the forward travel portion of Vtheir cycle of motion. Synchronized switching of the outputs of the. transducers effectively joins the physically discontinuous tracksto provide a continuous channel for storing data and providing access thereto. A more detailed discussion of both FiGS. 2a and 2b Will be made infra in the descrip-y tion of the switching arrangement and the specificwapparatus employed in the preferred embodiment illustrated inV Y FIGS. 5 to 7. In the Yforegoing discussion, the mechanical arrangement, i.e. the operating mechanism 27, has been set forth generally for producing phased cyclical movement ofaV i pair of movable transducers 20 and 24 for successively tracing helical tracks 4t) and 42 (FIG. 2a) on respective annular sections 18 and 22 of the outer annular periphery Y of the drum 10 by coordinating the rectilinear movements of the transducers with therotational movement Vof the drum. Switching means, including logical circuitryV shown in block form inV FIG. l, is `synchronized to be actuated with the movement of the operating mechanism 27 or movement of the transducers 20 and 24 and the drum 10 for switchingfrom one transducer, near the end Vof its forward travel, to the other transducer, begin-V ning its forward travel, to provide an endlessor continuous channel in a sequential access data store.

Timing signals i.e., clock and drum cycle signals, for

switching and for synchronization of information in the .f

dicate the beginning of a cycle of resolutionof the drumY 10. Circular track 43 has a closed series of timing signals, e.g., magnetically recorded signals having a sinusoidal Vwaveform to provide a continuous source of clock pulses C. Stationary read head46 and 47 are disposed adjacent to respective tracks 41 and 43 to detect the timing signals recorded in respective channels. The series of timing signals Vrecorded in track 43 and detected by readlhead l 47 are amplified by amplifier 73 to produce triggering signals c and c which are coupled to the true and false inputs of the flip-flop C having a true output providing a source of clock pulses C whose waveform is illustrated in FIG. 3a. The signal output of read head 46, illustrated in FIG. 3b, is coupled to amplifier 71a to provide input signals, FIGS. 3c and 3d, to and gates 7,1b andf71c, respectively, which Yproduce triggering signals x1 and 0x1. The triggering signals x1 and 0x1 are coupled to the true and false inputs of flip-flop X1. A true output of flip-nop X1 provides a source of drum cycle marker pulses X1, illustrated in FIG. 3e.

' In FIG. 4a, drum marker pulses X1 are shown in a scale smaller than shown in FIG. 3e. Additionalrtiming signals, illustratedV in FIG. 4b and 4c, are produced by a commutator 44 disposed coaxially on the cam shaft 34v to provide communtator signals S1 and S2 for synchronizing the switching of the output of theV read heads .and input to the Write heads, in read and write signal paths, with the movement of the transducers 20 and 24. Preferably, vthe leading edge of the communtator timing signals S1 or-S2 occurs midway between predetermined pairs of successive cycle marker pulses X1 to ensure'coincidence of one or the other of the occurring signals S1 or S2 and the latter drum cycle'marker pulse X1 of a pair.

The leading edges of the commutator signals S1 sup- 'plied by the commutator 44,1 are positioned in time to occur one-half cycle before the transducer24 reaches the end of its forward travel traversing the annular section 22, indicated by point 62 on the curve 53, in FIG. 2b; and

one-half cycle before the beginning of the forward travel of the transducer 20 traversing the annular section 1S, indicated yby the point 50 on curve S1. Generally, as may be noted iu the timing diagram of FIG. 2b, the phasing of the cycles of movements of the transducers 20 and 24, by adjustment of the angular positions of the disc cams 26 and 30, respectively, provides for one of the transducers 20 or 24 to Abegin its forward traversal of its respective section while the other is ending its -forward traversal. For similar reasons, the leading edges of the commutator timing signals S2 occur just prior to the end of the forward travel of transverse 20 over the annular section 18, indicated by point 54 on the cur-ve 51, and the beginning of the forward travel of the transducer 24 over the annular section 22, indicated -by point 60 on the curve v53.

The helical tracks 40 and 42, illustrated in FIG. 2a, are traced on the outer periphery of the dru-m 10 during the forward travel, at -a uniform rate, of the transducers 20 and 24, respectively. The helical tracks 40 and 42 begin at precisely located points 70a and 70b respectively, and end at precisely located points 74a and 74h, respectively, which points are synchnonized with the cycles of the drum 10 and the clock C. Since the cycle marker puls-e X1 indicates the beginning of each new cycle of the drum 10, the coincidence of the commutator timing signal S1, a drum cycle marker pulse X1, FIGS. 4b and 4a, and a clock pulse C in gate 72 will provide a triggering signal x2, FIG. 4d, at the true input of flip-flop X2 to produce the read switching signal X2, FIG. 4e, required to switch the common read signal output from the read head 84 positioned at the end of the helical track 42, to the read head 80 positioned at the beginning of the helical track 40. Coincidence of the commutator timing signal S2, FIG. 4c, a cycle marker pulse X1 and a clock pulse C in gate 7S will provide the triggering signal x2, FIG. 4d, to produce the read switching signal X2', FIG. 4f, required to switch the read signal output from read head 80 positoned at the end of the helical track 40, -to the read head `84 positioned at the beginning of the helical track 42.

Referring again to FIG. 1, for a description of .the circuit arrangement for producing timing signals, illustrated in FIGS. 3 and 4, for switching the common read signal output and the common write signal input for switching from one movable transducer to another, the amplifier 71a is coupled to the stationary read head 46 for amplifying the cycle marker signal, FIG. 3b, detected by the read head 46 at the beginning of each cycle of revolution of the drum 10. The cycle marker signal 45, recorded on the drum 10 along track 41, may comprise a substantially square magnetic saturation pattern or other magnetic pattern which induces signals of opposite polarity and spaced the width of the recorded cycle marker signal 45 in the transducer 46 and which signals when amplied in the amplifier 71 including a suitable output transformer will provide signals, illustrated in FIGS. 3c and 3d which are coupled to an gates 711i and 71e. Coincidence of the inputs to gates 71b and 71C with the clock pulses C produces the triggering'signals x1 and 0x1 which are coupled to true and false inputs, respectively, of the :Hip-flop X1. The true output of the flip-flop X1 provides drum cycle marker pulses X1, illustrated by typical waveforms in FIGS. 3e and 4a, which are coupled to both and gates 72 and 75. Coincident signals, including a clock pulse C, coupled to either gate 72 or gate 75 produce triggering signals x2 or 0x2 respectively, illustrated in FIG. 4d, at the respective true and false inputs of the flip-flop X2 to place the flip-flop X2 in its true and false states, respectively. The first triggering signal x2 or 0x2 of a series, during a single commutator timing signal S1 or S2, illustrated in FIG. 4d, is adequate to change the state of the iiip-ilop X2; and subsequent triggering signals, occurring within the same commutator signal period of S1 or S2, are ineffective. The time period of a commutator signal S1 or S2 need not be longer than one cycle of the drum in order to assure coincidence of the cycle marker pulse X1 and the commutator signals, 'S1 or S2. However, since the additional time of the period, i.e., three cycles of the drum, does not produce adverse effects in the operation, and the construction of the commutator is facilitated, the time period of the signals S1 and S2 Vis equal to lapproximately four cycles of the drum The read switching signals X2 and X2 on the true and false outputs of liip-ilop X2, illustrated in FIGS. 4e and 4f, are coupled to and gates 76 and 78 for sequentially switching the common read signal output of the memory Vfrom one read head to the other. The true and false out- Vputs of flip-flop X2 are also coupled to the delay circuit 79 and to gates 81 and 83, respectively, to provide, upon coincidence with clock pulses C, true and false triggering signals x3 and 0x3 for the true and false inputs, respectively, of the flip-flop X3, The write switching signals X3 and X3', from the true and false outputs of flip-flop X3are coupled to respective gates 104 and 105 for sequentially switching the write signals W1 from one write head to the other, one word period after switching of the common read signal output. In the preferred arrangement, v4the lateral separation of the heads is, for illustrative purposes, stated to be one word space; and, therefore, the delay in switching of the common write input including the delay of ilip-op X3 is one word period.

The delay circuit 79 may comprise recirculating line apparatus including write and read heads, for example, a stationary transducer 77a, shown in FIGS. 5 and 6, including a write head 77b and a read head 77e, which are disposed adjacent the upper end of the drum 10 above -a portion of a circular track 771. If the stationary transducer 77a is used for delay, the read and write heads 77b and 77c are spaced to delay the true and false outputs of ip-op X2 to effect a delay of one word period in changing the state of -ip-tlop X3 after a `change in the Ystate of ilip-liop X2.

The need for the delay in switching of the common write input from one write signal path to the other in order to couple the write signals W to the proper transducer write head lwill be apparent upon examination of the helical tracks 40 and 42, illustrated in FIG. 2a, and upon noting the lateral spacing of the heads in the detailed construction of the transducers 20 and 24, illustrated schematically in FIG. l, and shown in detail in FIGS. 5 and 7. The movable transducer 20 includes the read head S0 and the write head '82. The heads 80 and 82 are spaced circumferentially about the periphery of the drum 10 at a predetermined distance of one word space. `The spacing of read head 84 `and the write head 86 in transducer 24 is the same as the spacing of the read and write heads in the transducer 20. Individual read and write heads in a single movable transducer permit reading and writing simultaneously, while positioning of the read head before the write head along a helical track 40 or 42 provides advance examination of a data track for locating available spaces for writing by the write head spaced one word period behind the read head.

Referring now more particularly to FIG. 2a and 2b, the transducers 20 and 24 have been indicated schematically in the drawings to clarify the switching operation and the need for the delay in the switching of common write signal input to the write heads 82 and 86. The movable transducers 20 and 24 are indicated in FIG. .2n to be in positions in this case corresponding to the positions indicated by points 50 and 62, shown on the timing diagram in FIG. 2b. When the transducers 20 and 24 are located in the positions indicated in FIG. 2a, the read head in transducer 20 is positioned at the beginning of the helical track 40 and the read head 84 in transducer 24 is positioned at the end of the helical track 42. The switching of the common read signal output, from read head 84 to read head 80, discontinues the passing of data signals to the read signal output from the read conditions, as shown, the switching of the write signals W1 tothe Writerhead 82 should be delayed one word period at which time the write head 82 will reach point 70a; and concurrently, write head 86 will reach pointV 74b. As noted previously, the'spacing between read and Write heads in transducers 20 and 24 respectively is identical, and therefore, the time period of delay of switching is the same. In the preferred arrangement, the read and Write heads of .thetransducers are spaced one word period, and therefore, the time period of delay inswitching of the Write heads, after switching of read heads, is one word period. This need for delaying Vwill bemade more apparent upon considering the possibility of switching the read and write heads of transducers 20 and 24, simultaneously. This does not occur in the present arrangement but for purpose of explanation it is being considered. Simultaneous switching according to the hypothesis, would result in reading in the word space between the write and read heads at the end of the helical tracks 40 and 42 (FIG. 2a), in which word space no data hasV been written since the write heads have beenswitched priorvto passing over this word space; and, furthermore,

word space when it should be reading the data in theY word space Vbetween write head 82 and read head 80. As a result, the data written in the word space between write head S2 and read head 80 is never read and the n data storage channel is interrupted by one word space in vadditionato losing the data in the word space. The same analogy is applied to the word space at the endof track 40 and the beginning of track 42. Y 1

The signalV output of the read heads in transducers 20 and 24 are coupledV to a common output through individual read signal paths, and the Write heads are coupled to a common input source of write signals lthrough individual write signal paths. The data signals detected by the read heads 80 and 84 areV amplified by Yamplifiers 90 yand 92 respectively, individual to each read signal path. 'I'he amplified data signals in the output of theampliiier 90 are coupled to andgates 94 and 96 wherein the amplified data signal inputs are'individually gated by the separate clock pulse inputs C. The data signals passed by and gates 94 and 96 provide triggering signals r1 and r1 respectively for triggering the flip-nop R1. The output pulses R1 from the'true output of flip-flop R1 are coupled to the and gate 76 which passes read signals R1 when enabledV by a read switching signal X2, illustrated in FIG. 4e, as provided on the true output of the ip-op X2.

The amplified data signal output of the amplifier 92 is coupled to and gates 98 and 99, having clock pulse Y single output from the individualV paths for read signals from Vrespective read heads 80 and 84.

The individual write signal paths are provided for alternately coupling Write signals W1 to the write heads V82 and 86 in the movable transducers 20 and 24, respectively. The write signal input coupled to an amplifier 91 is amplied and coupled to Vgates 93 and 95 having clock pulse inputs to provide triggeringV signals w1 and w1 Vfor producing write signals W1 at the true output of the ipf op W1.

Referring to FIGS. 5 to 7 for a detailed'description of the mechanical arrangement of the preferred embodiment, a casing 120 as shown in'FIGS. 5 and 6 provides a partial enclosure for a major portion of theassembly, a mounting for motor 14, and supporting structure for the drum 10, operating means 27,.-and the movablef transducers 2G and`24. The drum 10 is coupled to the motor Y 'Y 14 by a belt `drive which rotates ,theV drfum at twice the speed of the Ymotor 14. The belt drive includes al belt 126, a pulley 128 secure-d to the upper en-d of the driveV movable transducers 20 and 24 is coupled ito the motor` v14 by a worm gear drive speed reduction unit 3,6 coupled to thecamshaft 34. :The disc cams`26 and SQYare mounted for rotation on camshaft 34 to actua-te the cam follower assembly by engaging the rollers 136 and 138, respectively. j Y

Referring now moreparticu-larly to FIG. 7 in` which the operating mechanism 27.is illustrated and the profilesV of the disc cams 26 and 30 are visible,'the individual cams 26 and 30 are mounted on the shaft 34 substantially 180 out of phase to impart the required motions to the follower assemblies,` lwhereby rotationV of the cams produces predetermined cyclical rectilinear motions to` the earn followers and transducers 20 and 24. The individual rectilinear motions-of the cam follower assemblies and transducers are illustrated in the timing diagram.

of FIG. 2b. Cam follower rollers -136Yand 138, which are offset from the follower rods 28 and 32, are connected to the follower rods by guiderarms 140 and 142, respec-Y tively. As shown, the arms 140 and 142 are secured to"l Y 26 and 30; and, generally, V'to inhibit rotation oft-he'cam` follower assembly thereby maintaining the alignmentF of the cam rollers 136 Vand 138 with the cams 26.and 30 lrespectively. K Y n p n A In the transformation of motion of rotation of the disc earns 26 and '30 to rectilinear motion of the carn follower rods 28 andV 32, respectively, the cam follower :assemblies are lifted by direct Contact of the rollers 1,36 land 138 and the respective cams. The upward vertical movement of the follower rods 28 and 32 or Vthe trans-V ducers 20` and 24 is denoted in FIG. 2b as theV forward travel; and the downwardmovement, as the return travel.

v A movable transducer which -has completed its forward travel returns to its initial or extreme .lower` position to complete a cycle of a motion which is then repeated. The

by anchor-ing to the lower side of the casing by suitable 9 fastening means 149. The upper portions of the springs 148 and 150 are secured to the respective rods by clamping brackets 152 and 154 which are secured to the ends of the springs by linkages 156 and 158, respectively.

The transducers 20 and 24 are secured to mounting blocks 160 and 162 by suitable fastening means to position the exposed heads adjacent the annular per-iphery 16 of the drum 10. The transducer mounting block 162 is connected to the follower rod 32 by a bracket 165 which is securely fitted on the rod 32, as shown, and coupled to the transducer mounting block 162 by a pin 166. The pin 166 is secured in the mounting block 162 to project laterally and pass through the transverse slot 168 provided in an arm 169 of the clamping bracket 165. Mounting block 160 is connected to rod 28 in the same manner as shown. These connections between the respective follower assemblies and the respective transducer mounting blocks transmit vertical motion of the followers to .the respective transducers 20 and 24 and their respective mounting blocks without transmitting possible lateral motions of the rods 28 and 32, and allows for greater tolerances in the Ifollower assembly guides and linkages permitting small movements laterally which do not affect the precise positioning of the transducer 24 along the outer annular periphery of the drum 10.

The transducers 20 and 24 and the mounting blocks 160 and 162 each bave vertical, centrally disposed openings to permit these members to be slidably supported on respective vertical shafts 170 and 171, provided for guiding the vertical movements of the transducers 20 and 24, respectively. Rotational movement of the transducers 20 and 24, and their mounting blocks 160 and 162, is inhibited by laterally projecting guide arms 172 and 173 respectively, secured to the respective mounting blocks 160 and 162. The ends of the guide arms 172 and 17'3 are moved up and down along vertical edges 176 and 177, respectively, of guide plates 174 and 175 which are secured to the respectivesides of the casing 120, as shown in FIGS. to 7. Spacer blocks 178 and 179 secured to the end portions of the lateral guide arm 172 and 173, respectively, are spring Urged to n'de along the vertical edges of the respective guide plates 174 and 175 by the tension of coil springs 180 and 181, each of which has one end connected to the respective guide arm by a suitably apertured bracket 182. The opposite ends of the springs 180 and 181 are coupled to the sides of the casing 120, as shown in FIG. 5.

The arrangements of the respective movable support assemblies for the transducer 20 and 24, coupling the transducers to the respective cam follower rods and including the vertical guide arrangement to prevent rotation, are substantially the same; however, it should be noted that the transducer 20 is secured to the bottom of the mounting block 160 whereas transducer 24 is disposed on top of block 162, and the support assemblies are disposed on opposite sides of respective cam follower rods. Positioning of the transducers 20 and 24, as shown, enables them to traverse the respective lower and upper annular sections 18 and 22 upon the actuation of operating means 27.

The commutator 44, which provides the commutator timing signals S1, S2 for switching between movable transducers 20 and 24, is shown in the exploded view portion of FIG. 7. The commutator 44 includes a continuous circular conductive stripk 186 and individual radially extending and integral commutating segments 188 and 190 secured concentrically on a circular. disc 191. The disc 191 is locked in position on the threaded end of the shaft 34 for synchronous movement with the shaft 34 by a nut 194, as shown. The commutator strip 186 is connected to ground by a brush 193, illustrated in FIG. 6. Commutator signals S1 and S2 are generated at brushes 195 and 197 .by the individual segments 188 and 190 engaging the brushes 195 and 197 during rotation of the disc 191. The brushes are supported by a block 196, and project therefrom to engage the circular strip 186 and respective contact segments.

Referring now more particularly to FIGS. S and 6, the stationary transducer 77a is shown to include a write head 77b and a read head 77e which are spaced to provide one word period between sequentially writing and then reading information on the portion of a track 77t between heads. The stationary transducer s employed for recirculating signals coupled to the write head 77b and taken 0E at the read head 77c. An identical stationary transducer 202 for recirculating signals is disposed on the opposite side of the drum 10 to cooperate with track 2021*. A stationary transducer assembly 204 is provided for supporting read heads 46 and 47 for reading drum cycle and clock timing signals recorded along tracks 41 and 43, respectively.

The operation will next be presented of the present invention, in which a continuous data store is provided by an arrangement in which a pair of transducers 20 and 24 are supported for transverse movement in respective operating zones 21 and 25 to cooperate with respective annular sections 18 and 22 yof the outer annular periphery bof the rotating drum 10. The traversals of the transducers 20 and 24 across sections 18 and 22, respectively, is indicated by the curves 51 and 53, respectively, in FIG. 2b. The transducers 20 and 24 alternately move upwardly traversing respective sections 18 and 22. This movement is indicated in FIG. 2b by the portions of the respective curves 51 and 53 between the points 50 and 54 and 60 and 62, respectively. During the period the transducer 20 traverses section 18 i.e., during the forward travel between points 50 and 54, the read signals coupled to and gate 76 from the read head 80 are coupled to the common read signal output through or gate and during the period the transducer 24 traverses section 22, i.e., during the forward travel between points y60 and 62, the read signals from read head 84 are passed by gates 78 and 100 to the common read signal output.

The write heads 82 and 86 alternately record the write signals coupled into the input of the amplifier 91. Write signals on the output of amplifier 91 are gated by clock signals C in the and gates 93 and 95 to provide triggering signal inputs w1 and w1 to the flip-flop W1. The write signals W1 provided on the output of the ip-ilop W1 are coupled to both gates 104 and 106. During the period of the forward travel of the transducer 20, the write signals W1 are passed by gate 104, amplified in amplifier 110, and coupled to the write head 82 which head records the write signals W1 in the helical track about section 18; and, during the period of the forward travel of transducer .24, the write signals W1 are passed by gate 106, amplified 1n amplifier 112, and coupled to the write head 86 which records the write signals W1 in the helical track about section 22.

c The commutator signals S1 and S2, FIGS. 4b and 4c, indicating the beginning of the forward travel of transducers 20 and 24, respectively, are derived from the commutator 44 which is disposed on the end of the camshaft 34 and is driven in synchronism with the disc cams 26 and 30. The commutator provides signals S1 and S2 indicative of predetermined radial sections of the disc cams 26 and 30 which correspond to predetermined rectilinear positions of the movable trans-ducers. Thus, the commutator 44 is capable of providing commutator signals S1 and S2 at the -beginning of the traversals of the annular section 18 and 22 by the transducers 20 and 24, respectively, by adjustment of the rotational position of the commutator disc 191 relative to the predetermined relative positions of the cams 26 and 30. The commutator disc is adjusted to produce signals S1 and S2 having leading edges occurring one-half a revolution of the drum before the beginning of the traversals of the sections 18 and 22 by the transducers 20 and 24, respectively. The beginning of the traversals of the annular sections 18 and 22 by the respective transducers 20 and 24 is indicated `tracks 40 and 42 are helical and begin at precisely located points 70a `and 7Gb which are positioned at the lower edges ofannular sections 18 and 22, respectively. The precise location of the points 70a and 70b about the circumference of the drum is resolved in the timing circuitry by drum cycle marker si-gnals derived from the Vdrum cycle marker channel having a signal 45 magnetically recorded in the circular track 41. The recorded cycle marker signal indicates the beginning of a new cycle or revolution of the drum 10. The typical output of the read head 46, in response to the cycle marker signal recorded on the drum, is illustrated by the'typical signal waveform as shown in FIG. 3b. The signal output of read head 46 is coupled to amplifier 71a providing enabling sig- -nals to gates 771b and 71C. The flip-flop X1 is controlled by triggering -signals x1 and 0x1 provided by gates 71b and 71C, as discussed supra, to produce cycle marker pulses X1, at the true output of hip-flop X1, illustrated in FIGS. 3e and 4a. Commutator signal S1 enables gate 72 and signal S2 enables gate 75 to provide triggering signals x2 and (1x2 upon coincidence of clock pulses C and cycle marker pulses X1 at the respective gates as illustrated by the typical waveforms in FIGS. 4a to 4d. The triggering signals x and x2 coupled to the true and false inputs of Hip-hop X2 produce switching signals X2 and X2', FIGS. 4e and 4f, at its true and false outputs.

Commutatorl signals S1 and S2 are adjusted in time to beginrapproximately midway between predetermined pairs of cycle marker pulses X1 to assure coincidence of a commutator signal S1 or S2 and the marker pulse X1 immediately'following the leading edge of the commutator signal. For example, as illustrated in FIGS. 4a and'4b, the leading edge 209 of the commutator signal S1 occurs midway between cycle marker pulses 208 and 210. The

true and false outputs of the flip-iiop X2 provide alten nately high potential switching signals X2 and X2 for the read heads 80 and 84, respectively. The switching signals X2 are coupled to gate 76 to pass the read signals from the read head 80 during forward travelof ,the transducer 20. The switchingl signals X'2 are coupled to the gate 78 to pass the read signals from the read head 84 during the forward travel of the transducer 24. Y

Since the read and write heads in each movable trans'- ducer and 24 are separated by one word space in the preferred arrangement, only the read heads 80 and 84 are positioned at the beginning of the respective tracks,

40 and 42 when the respective switching signals X2 and X2 initially rise to their high level; and the write heads 82 andY 86 do not reach the beginning of the respective tracks until one word period later. Therefore, the switching signals X3 and X'3 for the Write heads 82 and S6, respectively, are delayed one word period after switching the common read signal output to delay switching of the commonrwrite signal input until the write heads reach the beginning ofthe tracks 40 and 42 at points 70a and 70b, respectively. The true and false outputs of ip-op X2 are, therefore, coupled throughthe delay network 79 to be delayed one word period prior to coupling the outputs to respective gates 81 and 83. Clock pulses C coupled to gates 81 and 83 enable the gates to providetriggering signals x2 and 0x3 at the true and false inputs of ip-tlop X3. The true and false outputs of flip-flop X3 provide write'switching signals X3 and X'2 illustrated in FIGS. 4g and 4h, for the write heads 82 and 86 respectively, which are delayed one word period after read switching signals X2 and X2, respectively. Alternately, the write switchin'gsignals X3 and X'3 are at a'h'igh potential. lThe write switching signal X3 is coupled to and gate 104 to pass the write signals W1 to amplier 110k and write head 82 when the write head 82' reaches point 70a (FIG.

2a) at the beginning ofthe track 40; and the Write switch-Y ing signal X'3 is coupled to the and gate Y106 to pass the write signals W1 to the amplier 112 and the write head 86, when the write head 86 reaches vthe beginning of the track 42 at the point 70b.

The read switching signals X2 and X'2, illustrated in FIGS. 4e and 4f, are coupled to gates 76 and 78 respectively to alternately enable the gates 76 and 78 to pass the read signals R1 and R2, respectively, coupled thereto from respective read heads 80 and 84 through individual read signal paths. Since eitherv the read switching signal n X2 or X2" is at a high potential, alternate paths through nel in a sequential access data store, the combination com-Y either and gates 76 or 78 will provide'for a continuous flow of read signals from alternate read heads to the read signal Voutput of or gate 100.7The fand -gates 104 and 106 are alternately enabledby writing switching signals X3 and X3, respectively, illustrated in FIGS. 4g and 4hl to providek alternate paths" during predetermined time in-V tervals of signals X3 and X3 for a continuous flow of write signals W1 to the alternate write heads 82 and'86. Various modifications are'contemplated and may obviously be resorted to by those skilled in the art without departing from the spirit and scope of the invention, as hereinafter dened by the appended claims, as only a preferred embodiment thereof has been disclosed. For example, the data storage tracks 40 and'42 (FIG. 3) can be interlaced wherein the tracks are interposed instead of being separated in individual sections 18 and 22. However, an operating mechanism 29 would be required which would drive each ofthe movable transducers 21V and 24 Y.

to traverse the entire width of the outer annular periphery and three or more corresponding sections on three or more interlaced tracks. Additional modifications are numerous and oftenV more obvious, e.g., a continuous r'ec-V ,ord medium in the form of artape or belt and substitution of any other transducing system for storing information having a record medium and a transducer for reading'or writing information on the record medium.

What is claimed is: Y 1. In an arrangement for providing a continuous chanprising: data storage means comprising a'circular record member capable of storing data on an annular record surface thereof; transducing means including a plurality of transducers for cooperating with respectiveY tangentialV sections of said record surface for reading and writing data, each of said transducers comprising a set of spaced read and write heads and individual mounting means therefore to maintain read and write heads of each trans-- ducer in fixed spaced relationship relative to one another;

individually movable support means for each transducer provide frorroverlapping transverse movement of `said Y' mounting means whereby said read and write' heads ofV said plurality of transducers arepcapable of cooperating with the entire record surface of respective Ytangential sections of saidrecord surface including tangential areas of said sections; operating means individually coupled to each of said support means and to said record'member for producing relative movement of said record member and transducers to form distinct, substantially helical data tracks sequentially on the record surface during succesf sive alternate traversals by said read and write heads in l 13 face; and switching means coupled to said transducers for selecting the one transducer cooperating with its respective information track for reading and writing data continuously on alternate data tracks.

2. The combination according to claim 1 in which said operating means comprises disc cams individually coupled to respective ones of said support means for each transducer.

3. The combination according to claim 2 in which said individually movable support means comprises cam followers and guide means laterally spaced from said earn followers for maintaining the alignment of each of said cam followers on the periphery of said disc cams.

4. The combination according to claim 2 in which each of said disc cams have identically contoured periperal surfaces including sections of uniform contour disposed substantially 180 out-of-phase to impart uniform transverse movements to said support means alternately.

5. The combination according to claim 2 in which said operating means further includes a cam shaft for said disc cams and common drive means coupled to said cam shaft and said record member, and said switching means further includes commutation means comprising a commutator disc and brushes engaging said disc to produce two timing signals each cycle of revolution thereof to control the switching of respective ones of said transducers for cooperating with said record surface.

6. A sequential -access data store for providing an endless data storage channel, vsaid data store comprising: an annular rotatable record member having a record surface capable of storing data; transducing means including a pair of movable transducers, each including separate read and write heads disposed at a predetermined Xed distance relative to one another for cooperating with said record surface at a xed distance .along a single helical data track; individual support means circumferentially spaced about said record member for respective ones of said pair of transducers including means for providing for individual rectilinear movement of each transducer along respective circumferentially spaced paths having a direction transverse to the direction of rotation of said record member; operating means individually coupled to said support means for said transducers for cyclically and successively producing a uniform relative movement of alternate ones of said transducers along respective ones of said circumferentially spaced paths to cooperate with respective helical data tracks on said record surface and positioning the read head of one of the transducers at the beginning of its respective helical data track for reproducing data from said record surface when the read head of the other one of said transducers approaches the end of its respective data track; and cyclically operated switching means coupled to said pair of transducers for sequentially switching to the read head positioned at the beginning of its respective helical data track from the other read head positioned at the end of its respective data track to provide for a continuous, uninterrupted sequential iiow of data through the transducers during uniform relativnovement of one or the other of the read heads cooperating with said record surface along their respective data tracks.

7. The data store according to claim 6 in which each of said pair of transducers includes means for mounting said read and write heads of each transducer in a single enclosure and at a predetermined uniform word length spacing equal to a predetermined number of recorded binary signals in order to read and record binary signals of successive words simultaneously on said helical data tracks.

8. The data store according to claim 7 wherein said switching means is constructed and arranged to alternately switch both outputs and inputs of said read and write heads of the transducers to individually read and record on the record surface along respective data tracks during uniform movement of the read and write heads along -respective data tracks.

9. The data store according to claim 8 in which said switching means includes means for delaying the switching of the inputs to the write heads after switching the outputs of the read heads for a time interval equal to the time period required for the record member to move the distance between the read and write heads of the respective transducers. v

10. The data store according to claim 8 in which said switching means includes commutator means coupled to said operating means for producing lirst and second timing signals, each having a time duration of at least one cycle of revolution of said annular record member and occurring at the end of each uniform relative movement of respective ones of said transducers; cycle timing means coupled to said record member and producing a cycle pulse each revolution of said record member, each having a time duration equal to the time the record surface moves the distance of one word space between said read and write heads; clock timing means coupled to said record member for producing =a plurality of uniform spaced clock pulses during at least the time interval of said cycle pulse; and gating circuit means coupled to said commutator means, cycle timing means and clock timing means to produce switching signals for sequentially switching said transducers.

No references cited.

BERNARD KONICK, Primary Examiner. T. W, FEARS, Assistant Examiner. 

1. IN AN ARRANGEMENT FOR PROVIDING A CONTINUOUS CHANNEL IN A SEQUENTIAL ACCESS DATA STORE, THE COMBINATION COMPRISING: DATA STORAGE MEANS COMPRISING A CIRCULAR RECORD MEMBER CAPABLE OF STORING DATA ON AN ANNULAR RECORD SURFACE THEREOF; TRANSDUCING MEANS INCLUDING A PLURALITY OF TRANSDUCERS FOR COOPERATING WITH RESPECTIVE TANGENTIAL SECTIONS OF SAID RECORD SURFACE FOR READING AND WRITING DATA, EACH OF SAID TRANSDUCERS COMPRISING A SET OF SPACED READ AND WRITE HEADS AND INDIVIDUAL MOUNTING MEANS THEREFORE TO MAINTAIN READ AND WRITE HEADS OF EACH TRANSDUCER IN FIXED SPACED RELATIONSHIP RELATIVE TO ONE ANOTHER; INDIVIDUALLY MOVABLE SUPPORT MEANS FOR EACH TRANSDUCER DISPODED CIRCUMFERENTIALLY ABOUT SAID RECORD MEMBER FOR MOVEMENT ALONG CIRCUMFERENTIALLY SPACED PATHS, EACH OF SAID MOVABLE SUPPORT MEANS BEING CONSTRUCTED AND ARRANGED TO BE MOVED RECTILINEARLY TRANSVERSELY TO SAID RECORD SURFACE ALONG SAID CIRCUMFERENTIALLY SPACED PATHS TO PROVIDE FOR OVERLAPPING TRANSVERSE MOVEMENT OF SAID MOUNTING MEANS WHEREBY SAID READ AND WRITE HEADS OF SAID PLURALITY OF TRANSDUCER ARE CAPABLE OF COOPERATING WITH THE ENTIRE RECORD SURFACE OF RESPECTIVE TANGENTIAL 